Auto-injector

ABSTRACT

According to the invention, an auto-injector for administering a dose of a liquid medicament (M) comprises of a substantially cylindrical housing arranged to contain a pre-filled syringe filled with the medicament (M), a needle shroud slidably arranged with respect to the housing and adapted to rest on the skin of a patient receiving an injection, a releasable drive means arranged within the housing that is capable of, upon release, translating the needle shroud in a proximal direction (P) towards a safe position (PS) and a rotating collar rotatably arranged within the housing. The needle shroud in the safe position (PS) surrounds the injection needle after the injection has been carried out. The rotating collar engages the needle shroud in a manner that forces the rotating collar to rotate within the housing when the needle shroud is translated in the proximal direction (P).

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/909,107, filed on Jun. 23, 2020, which is a continuation ofU.S. patent application Ser. No. 15/669,571, filed on Aug. 4, 2017, nowU.S. Pat. No. 10,729,853, which is a continuation of U.S. patentapplication Ser. No. 13/993,528, with a 371 filing date of Jun. 12,2013, now U.S. Pat. No. 9,724,472, which is a U.S. National PhaseApplication pursuant to 35 U.S.C. § 371 of International Application No.PCT/EP2011/073502, filed Dec. 21, 2011, which claims priority toEuropean Patent Application No. 10196067.2, filed Dec. 21, 2010, andU.S. Provisional Patent Application No. 61/432,255, filed Jan. 13, 2011.The entire disclosure contents of these applications are herewithincorporated by reference into the present application.

TECHNICAL FIELD

The invention relates to an auto-injector for administering a dose of aliquid medicament.

BACKGROUND

Administering an injection is a process which presents a number of risksand challenges for users and healthcare professionals, both mental andphysical.

Injection devices (i.e. devices capable of delivering medicaments from amedication container) typically fall into two categories—manual devicesand auto-injectors.

In a manual device—the user must provide the mechanical energy to drivethe fluid through the needle. This is typically done by some form ofbutton/plunger that has to be continuously pressed by the user duringthe injection. There are numerous disadvantages to the user from thisapproach. If the user stops pressing the button/plunger then theinjection will also stop. This means that the user can deliver anunderdose if the device is not used properly (i.e. the plunger is notfully pressed to its end position). Injection forces may be too high forthe user, in particular if the patient is elderly or has dexterityproblems.

The extension of the button/plunger may be too great. Thus it can beinconvenient for the user to reach a fully extended button. Thecombination of injection force and button extension can causetrembling/shaking of the hand which in turn increases discomfort as theinserted needle moves.

Auto-injector devices aim to make self-administration of injectedtherapies easier for patients. Current therapies delivered by means ofself-administered injections include drugs for diabetes (both insulinand newer GLP-1 class drugs), migraine, hormone therapies,anticoagulants etc.

Auto-injectors are devices which completely or partially replaceactivities involved in parenteral drug delivery from standard syringes.These activities may include removal of a protective syringe cap,insertion of a needle into a patient's skin, injection of themedicament, removal of the needle, shielding of the needle andpreventing reuse of the device. This overcomes many of the disadvantagesof manual devices. Injection forces/button extension, hand-shaking andthe likelihood of delivering an incomplete dose are reduced. Triggeringmay be performed by numerous means, for example a trigger button or theaction of the needle reaching its injection depth. In some devices theenergy to deliver the fluid is provided by a spring.

US 2002/0095120 A1 discloses an automatic injection device whichautomatically injects a pre-measured quantity of fluid medicine when atension spring is released. The tension spring moves an ampoule and theinjection needle from a storage position to a deployed position when itis released. The content of the ampoule is thereafter expelled by thetension spring forcing a piston forward inside the ampoule. After thefluid medicine has been injected, torsion stored in the tension springis released and the injection needle is automatically retracted back toits original storage position.

SUMMARY

It is an object of the present invention to provide an improvedauto-injector.

The object is achieved by an auto-injector according to claim 1.

Preferred embodiments of the invention are given in the dependentclaims.

In the context of this specification, the terms distal and proximal aredefined from the point of view of a person receiving an injection.Consequently, a proximal direction refers to a direction pointingtowards the body of a patient receiving the injection and a proximal enddefines an end of an element that is directed towards the body of thepatient. Respectively, the distal end of an element or the distaldirection is directed away from the body of the patient receiving theinjection and opposite to the proximal end or proximal direction.

According to the invention, an auto-injector for administering a dose ofa liquid medicament comprises

a substantially cylindrical housing arranged to contain a pre-filledsyringe filled with the medicament,

a needle shroud slidably arranged with respect to the housing andadapted to rest on the skin of a patient receiving an injection,

a releasable drive means arranged within the housing that is capable of,upon release, translating the needle shroud in a proximal directiontowards a safe position and

a rotating collar rotatably arranged within the housing. The needleshroud in the safe position surrounds the injection needle after theinjection has been carried out. The rotating collar engages the needleshroud in a manner that forces the rotating collar to rotate within thehousing when the needle shroud is translated in the proximal direction.

A stopper may be arranged in the syringe barrel arranged to seal itsdistal end and to expel the dose of medicament. A coupling shroud may beslidably arranged within the housing and releasably coupled to a plungerthat is connected to the stopper. The drive means may be arrangedbetween a distal end of the housing and the coupling shroud to bias thecoupling shroud in a proximal direction towards the skin of a patientreceiving an injection.

The rotating collar creates friction to slow down a proximal movement ofthe needle shroud that rests on the skin of the patient during theinjection. The rotating collar acts as a dampening element thatalleviates the pressure exerted upon the skin of the patient by theneedle shroud that is driven by the drive means. Thus, the risk ofinjuries is reduced and, in particular, bruises may be avoided.Furthermore, the modulus of resilience of the single drive means may bechosen to be sufficiently large without having to worry about potentialinjury risks. Thus, the modulus of resilience of the drive means isadapted to reliably provide an energy supply for executing a pluralityof actions comprising, among others, the advancing and releasing of theneedle shroud, the displacement of the stopper to expel the medicamentand the decoupling of the plunger and the coupling shroud.

Preferably, the rotating collar comprises a pin that engages a helicalrecess formed into the needle shroud. The engagement of the helicalrecess and the pin forces the rotating collar to rotate around theneedle shroud when the needle shroud is translated. This dampens theproximal movement of the needle shroud and thus reduces the pressureexerted upon the skin of the patient by generating friction.

According to a possible embodiment of the invention, the needle shroudis slidable in a distal direction from an advanced position to arefracted position. In particular, the needle shroud may be slid to theretracted position by placing the auto-injector onto the skin of thepatient receiving the injection and pressing the needle shroud againstthe skin of the patient. The needle shroud in the retracted positionindicates the correct placement of the auto-injector. An activation of amechanism of the auto-injector delivering the medicament to the patientrequires the needle shroud to be positioned in the retracted position toensure that the auto-injector is properly used. The needle shroud isslidable in the proximal direction from the retracted position to thesafe position, wherein the needle shroud surrounds an injection needleof the pre-filled syringe to prevent accidental needle stick injuriesafter the injection has been carried out.

According to another possible embodiment of the invention, the drivemeans is arranged to be released by manual actuation of a releaseelement that is hinged to a lateral side of the housing. Conventionalauto-injectors are commonly activated by actuating a push button or thelike arranged at a distal end of the auto-injector. An inexperienceduser of such a conventional auto-injector may easily mistake the distalend for a proximal end of the auto-injector and thus may pierce hisfinger while trying to actuate the auto-injector. The lateralarrangement of the release element is a simple means to prevent suchaccidental needle stick injuries resulting from a misuse of theauto-injector.

Alternatively, the release element is in slidable arrangement with thehousing and may be translated with respect to the housing in theproximal direction to release the drive means. The auto-injectoraccording to this embodiment of the invention is particularly intuitiveto operate.

According to another possible embodiment of the invention, theauto-injector comprises safety means that cooperate with the needleshroud that is arranged to prevent a release of the drive means when theneedle shroud is in the advanced position and hence is not pushedagainst the skin of the patient. This mechanism avoids an early releaseof the drive means and thus a premature expelling of the medicament.Furthermore, injuries resulting from an activation of the drive meanswhen the auto-injector is not placed, or not properly placed onto theskin of the patient are reduced.

The safety means may comprise a blocking element slidably arrangedrelative to the housing. The blocking element is arranged to limit apivoting movement of the release element hinged to the lateral side ofthe housing when the needle shroud is in the advanced position. Arelease of the drive means is thus prevented. The release element isallowed to pivot about the hinge when the needle shroud is moved to theretracted position by pressing the needle shroud against the skinsurface of the patient receiving the injection.

In one possible embodiment of the invention, the safety means comprisesan elastic bushing that engages a plunger of the pre-filled syringeand/or a coupling shroud that is biased by the drive means and coupledto the plunger of the pre-filled syringe. The elastic bushing is firmlyattached to a proximal end of the housing and may engage the couplingshroud and/or the plunger to prevent an inadvertent release of the drivemeans.

In another preferred embodiment of the invention, the drive means iscapable of, upon release, driving the coupling shroud releasably coupledto the plunger from a first position in the proximal direction. Thecoupling shroud is driven by the drive means to interact with differentcomponents of the auto-injector, so that the resilient force provided bythe drive means may be used to power a variety of functions of theauto-injector. The proximal translatory movement of the coupling shroudwith respect to the housing

translates a syringe retainer receiving the pre-filled syringe in theproximal direction to expose the injection needle of the pre-filledsyringe,

depresses the plunger connected to a stopper into the syringe barrel toexpel the dose of medicament and

translates the needle shroud in the proximal direction. The couplingshroud mediates the resilient force provided by the drive means to thisvariety of different components of the auto-injector and thus allows fora compact design of the auto-injector. In particular, the auto-injectormay be powered by just a single drive means to accomplish a plurality oftasks necessary for safely carrying out the injection.

According to yet another possible embodiment of the invention, thesyringe retainer is releasably mounted to the housing. The needle shroudin the retracted position releases the syringe retainer to allow for theproximal translation of the syringe retainer with respect to thehousing. Thus, a proximal movement of the syringe retainer that inparticular inserts the injection needle into the skin of the patient isprevented until the auto-injector is correctly placed upon the skin ofthe patient and the needle shroud is pushed against the skin surfacetowards the retracted position. This prevents an inadvertent earlyrelease of the drive means.

The coupling shroud is initially in a first position, and coupled to theplunger to translate the syringe retainer proximally, whereby theinjection needle is inserted into the skin of the patient, and todepress the stopper into the syringe barrel to expel the medicament. Theplunger and the coupling shroud are decoupled from each other at theproper pre-determined second position after the medicament has beencompletely or partially delivered. The pre-determined second position isdefined by a longitudinal aperture in the housing.

According to another possible embodiment of the invention, a couplingcatch is arranged to abut against a shoulder formed to the plunger as aparticularly simple and reliable means to releasably couple the plungerto the coupling shroud. The coupling shroud is moved by the action ofthe relaxing drive means in the proximal direction and is coupled to theplunger connected to the stopper to insert the injection needle beforethe injection and to expel the medication during the injection.

The aperture formed into the lateral side of the housing at the secondposition allows the coupling catch to deflect radially outwards at thesecond position, so that the coupling shroud is decoupled from theplunger after the medicament is partially or completely delivered.

Preferably, the drive means is arranged as a single compression spring.The mechanism of the auto-injector is arranged in a manner that aplurality of functions is executed by the single drive means. Theinjection needle is inserted into the skin of the patient, the plungeris translated to expel the medicament and the needle shroud is movedproximally to provide needle safety after the injection is completed bythe action of the spring means. Conventional auto-injectors usuallycomprise a plurality of spring means to accomplish these tasks. Theauto-injector according to the invention comprises only few parts and isparticularly inexpensive to mass-produce. Consequently, theauto-injector is particularly suited as a single-use device that may bedisposed after an injection has been carried out.

The auto-injector may preferably be used for subcutaneous orintra-muscular injection, particularly for delivering one of ananalgesic, an anticoagulant, insulin, an insulin derivate, heparin,Lovenox, a vaccine, a growth hormone, a peptide hormone, a proteine,antibodies and complex carbohydrates.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus, are not limitiveof the present invention, and wherein:

FIGS. 1A and 1B show two different sectional views of an auto-injectoraccording to a first embodiment of the invention with a hinged releaseelement before an injection,

FIG. 2 is an expanded sectional view of the auto-injector according tothe first embodiment, wherein the release element is blocked to preventan inadvertent release of a drive means,

FIG. 3 is an expanded sectional view of the hinged release element thatis actuated to release the drive means,

FIGS. 4A and 4B are two different sectional views of the auto-injectoraccording to the first embodiment after a drug has been delivered,

FIG. 5 is an isometric view of a needle shroud,

FIGS. 6A and 6B are two different sectional views of the auto-injectoraccording to the first embodiment after an injection has been performed,

FIGS. 7A and 7B are two different sectional views of an auto-injectoraccording to a second embodiment of the invention,

FIG. 8 is a sectional view of a distal end section of the auto-injectoraccording to the second embodiment of the invention,

FIGS. 9A and 9B are two different sectional views of an auto-injectoraccording to a third embodiment of the invention,

FIG. 10 is a sectional view of a distal end section of the auto-injectoraccording to the third embodiment of the invention.

Corresponding parts are marked with the same reference symbols in allfigures.

DETAILED DESCRIPTION

FIGS. 1A and 1B show two sectional views of an essentially cylindricalauto-injector 1 according to a first embodiment of the invention,wherein the sectional plane shown in FIG. 1A is oriented perpendicularlyto the one shown in FIG. 1B. The auto-injector 1 comprises a housing 2,a proximal needle shroud 3, a syringe retainer 4 adapted to mount andmove translatably with a pre-filled syringe 5 within the housing 2, acoupling shroud 6 slidably arranged within the housing 2 and a releaseelement 7 hinged to a lateral side of the substantially cylindricalhousing 2 of the auto-injector 1.

A single drive means 8 is arranged between the distal end of the housing2 and the coupling shroud 6 to bias the coupling shroud 6 in a proximaldirection P towards the skin of a patient receiving an injection.

According to one possible embodiment of the invention, the drive means 8is arranged as a single, conventional compression spring.

The coupling shroud 6 is releasably coupled to a plunger 9 that isconnected to a stopper 10 fluid-tightly sealing a distal end of asyringe barrel 11 containing a dose of a medicament M. An inner cavityof the syringe barrel 11 is in fluid communication with an injectionneedle 12, so that the dose of the medicament M may be expelled throughthe injection needle 12 by displacing the stopper 10 in the proximaldirection P.

Before the injection, the coupling shroud 6 abuts against a distal endof the release element 7 to releasably retain the coupling shroud 6 in afirst position I, wherein the coupling shroud 7 is located at a distalend of the housing 2. The drive means 8 is compressed, so that thecoupling shroud 6 is strongly biased in the proximal direction P.

The plunger 9 extends from the syringe barrel 11 in a distal direction Dand comprises a shoulder 9.1 of increased diameter. The coupling shroud6 comprises an inwardly protruding coupling catch 6.1 that bears againstthe shoulder 9.1 so that the plunger 9 and the coupling shroud 6 may bejointly moved in the proximal direction P by the action of the relaxingdrive means 8.

The proximal end of the needle shroud 3 is designed to be pushed againstthe skin surface of the patient during the injection. Edges of theneedle shroud 3 may thus be smoothed to avoid injuries. The needleshroud 3 is slidably arranged within the housing 2 of the auto-injector1, so that the needle shroud 3 may be pushed from an advanced positionPA shown in FIGS. 1A and 1B in the distal direction D. A biasing means13 bears against the needle shroud 3 and the housing 2 to bias theneedle shroud 3 towards the advanced position PA.

An annular rotating collar 14 engages an outer surface of the needleshroud 3. The rotating collar 14 rotates around an axis of thesubstantially cylindrical auto-injector 1 when the needle shroud 3 islongitudinally displaced in the proximal and/or the distal direction P,D. The rotating collar 14 acts as a damping means that creates frictionto slow down the movement of the needle shroud 3 and to reduce thepressure exerted onto the skin of the patient receiving the injection.

The release element 7 hinged to the housing 2 works like a see-saw: aproximal section may be pushed radially inwards, whereby the releaseelement 7 pivots about a hinge 15, so that the distal section of therelease element 7 moves radially outwards and the coupling shroud 6 isdisengaged to release the drive means 8.

The auto-injector 1 comprises safety means S that prevent an earlyrelease of the drive means 8. The safety means S ensure that the needleshroud 3 is pushed against the skin of the person receiving theinjection before the drive means 8 may be released.

According to the first embodiment of the invention, the safety means Scomprise a blocking element 16 slidably arranged with the housing 2.When the needle shroud 3 is positioned in the advanced position PA, theblocking element 16 is positioned to prevent a pivoting movement of therelease element 7 and thus a release of the coupling shroud 6. Aradially outwards protruding blocking projection 16.1 of the blockingelement 16 is located opposite to an inward protrusion 7.1 formed to therelease element 7. If the proximal section of the release element 7 ispushed inwards, the inward protrusion 7.1 abuts against the blockingprojection 16.1 to limit the pivoting movement of the release element 7,so that a release of the coupling shroud 6 and the drive means 8 isprevented.

FIG. 2 shows a proximal section of the auto-injector 1 in a sectionalview with the blocking element 16 positioned to prevent an inadvertentactuation of the hinged release element 7 to release the drive means 8.

A distal end of the needle shroud 3 is clipped to the housing 2 andretained between two inwardly protruding retaining protrusions 2.1formed into an inner surface of the housing 2. The two retainingprotrusions 2.1 are longitudinally displaced from each other to limitthe range of axial displacement of the needle shroud 3 with respect tothe housing 2. A boss 3.1 formed into an outer surface of the needleshroud 3 bears against an inner surface of the blocking element 16, sothat the blocking element 16 may move with the needle shroud 3 in theproximal direction P to deblock the release element 7.

The blocking projection 16.1 comprises a central indention that forces auser of the auto-injector 1 to perform a sequence of actions necessaryto inject the dose of the medicament M in the proper order. If therelease element 7 is pushed inwards before the needle shroud 3 is movedproximally from the advanced position PA towards a retracted position PR(see FIG. 3) by pushing the needle shroud 3 towards the skin of thepatient, the inward projection 7.1 is retained in the centralindentation of the blocking projection 16.1, so that both thelongitudinal displacement of the needle shroud 3 and the pivotingmovement of the release element 7 is blocked.

A proper sequence of actions for injecting the dose of the medicament Mis described in the following. First, the user pushes the needle shroud3 against the skin to move the needle shroud 3 distally to the retractedposition PR illustrated in FIG. 3. The blocking element 16 jointly moveswith the needle shroud 3 in the distal direction D, so that the releaseelement 7 may be manually actuated to pivot about the hinge 15, wherebythe drive means 8 are released.

Upon release of the drive means 8, the coupling shroud 6 is urged in theproximal direction P. The single and fully compressed drive means 8drives the coupling shroud 6 and the plunger 9 coupled thereto in theproximal direction P. The coupling shroud 6 first pushes the syringeretainer 4 by means of plunger 9, stopper 10 and the friction betweenstopper 10 and syringe 11 proximally to insert the injection needle 12into the skin of the patient and a first clip connection 2.2 formed intoa lateral side of the housing 2 latches to an outward protrusion 4.1 ofthe syringe retainer 4, as illustrated in more detail in FIG. 4B.

The syringe retainer 4 and the pre-filled syringe 5 mounted thereto isnow locked to the housing 2. The coupling shroud 6 is moved further inthe proximal direction P by the action of the relaxing drive means 8,whereby the plunger 9 is depressed into the syringe barrel 11 to expelthe dose of the medicament M contained therein through the injectionneedle 12.

FIGS. 4A and 4B show two sectional views of the auto-injector 1according to the first embodiment of the invention with the plunger 9fully depressed within the syringe barrel 11. The dose of the medicamentM has been delivered beneath the skin of the patient. The couplingshroud 6 is located in an intermediate second position II. The drivemeans 8 is not yet completely discharged and biases the coupling shroud6 in the proximal direction P. The shoulder 9.1 engages a ramp of thecoupling catch 6.1 to deflect the coupling catch 6.1 in a radial outwarddirection. An aperture 2.3 is formed into the housing 2 to allow for aradial outward deflection of the coupling catch 6.1, so that thecoupling catch 6.1 overcomes the shoulder 9.1 decoupling the couplingshroud 6 from the plunger 9.

In a possible embodiment of the invention, the aperture 2.3 defining thesecond position II is located at a longitudinal position along thehousing 2 that allows for a full depression of the plunger 9 completelyemptying the syringe barrel 11 before the plunger 9 is decoupled fromthe coupling shroud 6.

Alternatively, the aperture 2.3 defining the second position II may belocated at a longitudinal position along the housing 2 that allows foran adjustment space accounting for manufacturing tolerances. Theadjustment space is dimensioned as to allow for a reliable decoupling ofthe plunger 9 from the coupling shroud 6 even if the parts constitutingthe auto-injector 1 comprise mismatch in mould or are slightlymisaligned. In this alternative embodiment, the dose of the medicament Mmay or may not be completely expelled before the plunger 9 is decoupledfrom the coupling shroud 6.

The retaining protrusions 2.1 are elastically supported and may bedeflected radially outwards to release the needle shroud 3. The couplingshroud 6 engages a ramp of the retaining protrusions 2.1 and splays theretaining protrusions 2.1 outwards, whereby the needle shroud 3 isreleased and allowed to move proximally from the retracted position PRtowards an extended safe position PS.

The drive means 8 is still partially loaded when the coupling shroud 6is located in the second position II. In a possible embodiment of theinvention the biasing force of the drive means 8 exerted on the couplingshroud 6 in the second position II is about 10 N.

The coupling shroud 6 bears against a distal end of the needle shroud 3,so that the needle shroud 3 may be moved to the safe position PS by theaction of the further relaxing drive means 8. As the biasing forceexerted onto the needle shroud 3 by the drive means 8 may be relativelylarge and could even bruise the patient, the rotating collar 14 isarranged within the housing 2 to partially absorb the excess energy ofthe drive means 8 and slow down the proximal movement of the needleshroud 3 by generating friction.

FIG. 5 shows an isometric view of the needle shroud 3. A helical recess3.2 is formed into a tubular proximal section 3.3 of the needle shroud3. The proximal section 3.3 of the needle shroud 3 is inserted into theannular rotating collar 14, wherein a pin 14.1 formed to an innersurface of the rotating collar 14 protrudes into the helical recess 3.2as shown in FIG. 6A. The linear translatory movement of needle shroud 3towards the safe position PS thus causes the rotating collar 14 torotate within the housing 2 around the axis of the auto-injector 1.

FIGS. 6A and 6B show two different sectional views of the auto-injector1 according to the first embodiment of the invention after the injectionhas been performed. The needle shroud 3 is permanently locked to thesafe position PS by a second clip connection 2.4 formed into the housing2. The needle shroud 3 surrounds the injection needle 12 and extends asuitable distance proximally beyond the needle tip to avoid accidentalneedle stick injuries after the auto-injector 1 has been used.

FIGS. 7A and 7B show two different sectional views of an auto-injector 1according to a second embodiment of the invention before the injection.The sectional plane shown in FIG. 7A is oriented perpendicularly to thesectional plane shown in FIG. 7B.

The needle shroud 3 of the auto-injector 1 according to the secondembodiment substantially extends over the axial length of the housing 2.Before the injection, the needle shroud 3 is mounted to the housing 2 bythe retaining protrusions 2.1 that protrude into orifices formed into alateral side of the needle shroud 3. The orifices comprise alongitudinal length that allows the needle shroud 3 to be slid from theadvanced position PA to the retracted position PR.

A retaining catch 2.5 is formed to an inner surface of the housing 2 andprotrudes through an opening formed into the needle shroud 3 toreleasably mount the syringe retainer 4 retaining the pre-filled syringe5. The retaining catch 2.5 comprises a bevelled ramp and is deflectablein a radial outward direction. The retaining catch 2.5 latches to theoutward protrusion 4.1 formed to the outer surface of the syringeretainer 4 when the needle shroud 3 is in the advanced position PA

The needle shroud 3 abuts against the bevelled ramp of the retainingcatch 2.5 when the needle shroud 3 is moved from the advanced positionPA in the distal direction D, whereby the retaining catch 2.5 isdeflected in a radial outward direction and disengages the outwardprotrusion 4.1, so that the syringe retainer 4 may be moved in theproximal direction P.

The release element 7, shown in more detail in FIG. 8, is arranged as apush button and mounted to a distal end of the housing 2. The releaseelement 7 may be pushed in the proximal direction P to release the drivemeans 8 when the needle shroud 3 is in the retracted position PR,whereas the release element 7 and thus the release of the drive means 8is blocked when the needle shroud 7 is in the advanced position PA.

According to the second embodiment of the invention, the safety means Sthat prevent the early release of the drive means 8 comprises clips 2.6that may deflect in a radial outward direction and a bushing 17 lockingthe plunger 9 before use of the auto-injector 1.

Before the auto-injector 1 is used, the clips 2.6 formed to the housing8 latch to the release element 7. (See FIG. 7B) The clips 2.6 block themovement of the release element 7 in the proximal direction P, so that amanual actuation of the release element 7 is prevented as long as theneedle shroud 3 is in the advanced position PA. A distal movement of therelease element 7 is blocked by a first detent 2.7 engaging an innersurface of the release element 7.

The clip 2.6 comprises a ramp that the needle shroud 3 engages whenpushed distally from the advanced position PA to the refracted positionPR, whereby the clip 2.6 is deflected radially outwards to disengage theneedle shroud 3. The release element 7 may be pushed in the proximaldirection P when the needle shroud 3 is in the retracted position PR.

The plunger 9 comprises a distal end 9.2 of increased diameter that isretained in the bushing 17 firmly attached to a distal end of thehousing 2. The bushing 17 comprises an inner surface corresponding tothe distal end 9.2 of the plunger 9 that engages the distal end 9.2 in alocked position L to lock the plunger 9 and the coupling shroud 6coupled thereto to the housing 2 before use of the auto-injector 1. Thebushing 17 abuts radially against an annular inner collar 7.2 of therelease element 7 in the locked position L shown in FIGS. 7A and 7B. Aradial outward deflection of the bushing 17 releasing the plunger 9 isthus prevented.

FIG. 8 shows a sectional view of a distal end section of theauto-injector 1 according to the second embodiment of the invention. Theneedle shroud 3 is located in the retracted position PR and the releaseelement 7 is pushed in the proximal direction P, so that the bushing 17disengages the annular inner collar 7.2 of the release element 7. Thebushing 17 is positioned in an unlocked position U and may deflectoutwardly to release the plunger 9.

Furthermore, the bushing 17 acts as a counter bearing for the drivemeans 8 bearing against the bushing 17 in the distal direction D.

FIGS. 9A and 9B show two different sectional views of an auto-injector 1according to a third embodiment of the invention, wherein the releaseelement 7 is arranged as an outer sleeve extending over a substantiallength of the auto-injector 1.

According to the third embodiment of the invention, the safety means Sthat prevent the early release of the drive means 8 comprise clips 2.6,second and third detents 2.8, 7.3, a locking catch 6.2 formed to thecoupling shroud 6 and the bushing 17 that comprises an inner sleeve 17.1receiving a lug 7.4, wherein the locking catch 6.2 latches to a collar17.2 of the inner sleeve 17.1.

The release element 7 of the third embodiment is gripped by a user toperform the injection. When the needle shroud 3 is in the advancedposition PA, the proximal displacement of the release element 7 isblocked by the clips 2.6 in a similar manner as in the second embodimentdescribed herein above.

Additionally, the release element is releasably retained in positionbefore the injection by the second and the third detents 2.8, 7.3respectively formed to an outer surface of the housing 2 and to an innersurface of the release element 7, wherein the second and third detents2.8, 7.3 comprise correspondingly shaped ramps facing each other.

The bushing 17 of the third embodiment comprises the inner sleeve 17.1that receives the lug 7.4 formed to an inner surface of the releaseelement 7. A proximal end of the lug 7.4 snugly fits in the centralaperture of the inner sleeve 17.1, so that an inward deflection of theinner sleeve 17.1 is prevented.

The inner sleeve 17.1 comprises a collar 17.2. An inwardly protrudinglocking catch 6.2 of the coupling shroud 6 latches to the collar 17.2before use of the auto-injector 1 to releasably retain the couplingshroud 6 in the first position I.

FIG. 10 shows a sectional view of a distal end section of theauto-injector 1 according to the third embodiment of the invention. Therelease element 7 is actuated and moved in the proximal direction P. Theproximal end of the lug 7.4 disengages the inner sleeve 17.1 of thebushing 17, so that the inner sleeve 17.1 may bend radially inwards,whereby the locking catch 6.2 disengages the collar 17.2 and releasesthe coupling shroud 8 and the drive means 8.

The invention claimed is:
 1. An auto-injector comprising: a cylindricalhousing containing a syringe that contains a medicament, the syringecomprising a stopper slidably disposed within a body of the syringe, thestopper forming a fluid tight seal with the body of the syringe; aplunger rod configured to engage the stopper for dispensing themedicament from the syringe; a compression drive spring configured tobias the plunger rod in a proximal direction to dispense the medicamentfrom the syringe; a needle shroud comprising a proximal end portionterminating in an annular flange and two arms extending distally fromthe proximal end portion, the needle shroud defining an opening thatreceives an inward projection that projects inwardly from an innersurface of the cylindrical housing, and the needle shroud being slidable(i) in a distal direction relative to the cylindrical housing from anadvanced position to a retracted position and (ii) in the proximaldirection relative to the cylindrical housing from the retractedposition to a locked position, wherein a proximal end of the needleshroud proximally extends beyond a proximal end of an injection needleof the syringe when the needle shroud is in the advanced position, theproximal end of the injection needle proximally extends beyond theproximal end of the needle shroud when the needle shroud is in theretracted position, and the proximal end of the needle shroud proximallyextends beyond the proximal end of the injection needle when the needleshroud is in the locked position; a needle shroud spring configured tobias the needle shroud in the proximal direction relative thecylindrical housing; an annular rotating collar rotatably arrangedwithin the cylindrical housing, the annular rotating collar beingconfigured to engage the needle shroud in a manner such that a distaltranslation of the needle shroud causes a pin to ride along a trackthereby causing the annular rotating collar to rotate about alongitudinal axis of the cylindrical housing; a sleeve comprising aflexible arm having an angled surface that is configured to bereleasably coupled to the plunger rod, the sleeve having a first statein which the angled surface of the flexible arm is held in engagementwith a surface of the plunger rod to prevent the plunger rod from movingproximally under a force of the compression drive spring, and the sleevehaving a second state in which the angled surface of the flexible arm isoutwardly deflected out of engagement with the surface of the plungerrod to allow the plunger rod to move proximally under the force of thecompression drive spring to dispense the medicament; and a syringeretainer disposed within the cylindrical housing, the syringe retainerdefining a cavity in which the syringe is disposed, the syringe retainercomprising an inwardly angled protrusion that is located at a proximalend of the syringe retainer and that is engaged with a proximal end ofthe body of the syringe, the syringe retainer being sized such that adistal end of the syringe extends distally beyond a distal end of thesyringe retainer and a distal flange of the syringe is distally spacedapart from the syringe retainer while the proximal end of the body ofthe syringe is engaged with the inwardly angled protrusion of thesyringe retainer, a distal portion of the syringe retainer comprising anoutward protrusion extending outward from an outer surface of thesyringe retainer, and the syringe retainer being engaged with an inwardprotrusion of the cylindrical housing to limit proximal movement of thesyringe retainer relative to the cylindrical housing.
 2. Theauto-injector of claim 1, wherein the inward protrusion of thecylindrical housing is integrally formed with the cylindrical housing.3. The auto-injector of claim 2, wherein the syringe retainer isconfigured to slide relative to the cylindrical housing in the proximaldirection until the syringe retainer engages the inward protrusion ofthe cylindrical housing at which point further proximal movement of thesyringe retainer relative to the cylindrical housing is prevented. 4.The auto-injector of claim 2, wherein the inward protrusion of thecylindrical housing extends from a proximal portion of the cylindricalhousing.
 5. The auto-injector of claim 2, wherein only the inwardlyangled protrusion of the syringe retainer retains the syringe in theproximal direction.
 6. The auto-injector of claim 1, wherein the outwardprotrusion of the syringe retainer is configured to releasably engage aflexible arm of the cylindrical housing when the syringe retainer is ina distal position within the cylindrical housing.
 7. The auto-injectorof claim 1, wherein the inwardly angled protrusion of the syringeretainer is configured to retain the syringe in the proximal directionrelative to the syringe retainer.
 8. The auto-injector of claim 1,wherein the surface of the plunger rod is a shoulder configured toengage the angled surface of the flexible arm of the sleeve.
 9. Theauto-injector of claim 1, wherein the surface of the plunger rod definesa recess configured to receive the angled surface of the flexible arm ofthe sleeve.
 10. The auto-injector of claim 1, wherein the auto-injectoris configured such that as the needle shroud slides in the proximaldirection from the retracted position to the locked position, the needleshroud engages a ramp.
 11. The auto-injector of claim 10, wherein theauto-injector is configured such that as the needle shroud slides in theproximal direction from the retracted position to the locked position,the needle shroud proximally slides over the ramp, and distal movementof the needle shroud relative to the cylindrical housing is preventedafter the needle shroud has proximally slid over the ramp.
 12. Theauto-injector of claim 1, wherein when the sleeve is in the first state,a flexible arm retaining surface engages the flexible arm to hold theangled surface of the flexible arm in engagement with the surface of theplunger rod, and when the sleeve is in the second state, the flexiblearm is allowed to deflect in an outward direction into a void.
 13. Theauto-injector of claim 12, wherein the flexible arm of the sleeve isconfigured to move relative to the void when the sleeve transitions fromthe first state to the second state.
 14. The auto-injector of claim 1,wherein the syringe contains a single dose of the medicament.
 15. Theauto-injector of claim 1, wherein the sleeve is attached to a distal endof the cylindrical housing.
 16. The auto-injector of claim 1, wherein adistal end of the auto-injector does not include a push-button.
 17. Anauto-injector comprising: a cylindrical housing containing a syringethat contains a medicament, the syringe comprising a stopper slidablydisposed within a body of the syringe, the stopper forming a fluid tightseal with the body of the syringe; a plunger rod configured to engagethe stopper for dispensing the medicament from the syringe; acompression drive spring configured to bias the plunger rod in aproximal direction to dispense the medicament from the syringe; a needleshroud slidable (i) in a distal direction relative to the cylindricalhousing from an advanced position to a retracted position and (ii) inthe proximal direction relative to the cylindrical housing from theretracted position to a locked position; a needle shroud springconfigured to bias the needle shroud in the proximal direction relativethe cylindrical housing; an annular rotating collar rotatably arrangedwithin the cylindrical housing, the annular rotating collar beingconfigured to engage the needle shroud in a manner such that a distaltranslation of the needle shroud causes the annular rotating collar torotate about a longitudinal axis of the cylindrical housing; a sleevecomprising a flexible arm having a surface that is configured to bereleasably coupled to the plunger rod, the sleeve having a first statein which the surface of the flexible arm is held in engagement with asurface of the plunger rod to prevent the plunger rod from movingproximally under a force of the compression drive spring, and the sleevehaving a second state in which the surface of the flexible arm isdeflected in an outward direction to allow the plunger rod to moveproximally under the force of the compression drive spring to dispensethe medicament; and a syringe retainer disposed within the cylindricalhousing, the syringe retainer defining a cavity in which the syringe isdisposed, the syringe retainer comprising an inwardly angled protrusionthat is located at a proximal end of the syringe retainer and that isengaged with a proximal end of the body of the syringe, the syringeretainer being sized such that a distal end of the syringe extendsdistally beyond a distal end of the syringe retainer and a distal flangeof the syringe is distally spaced apart from the syringe retainer whilethe proximal end of the body of the syringe is engaged with the inwardlyangled protrusion of the syringe retainer.
 18. The auto-injector ofclaim 17, wherein the surface of the flexible arm is out of engagementwith the surface of the plunger rod when the sleeve is in the secondstate.
 19. The auto-injector of claim 17, wherein a proximal end of theneedle shroud proximally extends beyond a proximal end of an injectionneedle of the syringe when the needle shroud is in the advancedposition, the proximal end of the injection needle proximally extendsbeyond the proximal end of the needle shroud when the needle shroud isin the retracted position, and the proximal end of the needle shroudproximally extends beyond the proximal end of the injection needle whenthe needle shroud is in the locked position.
 20. The auto-injector ofclaim 17, wherein sliding of the needle shroud in the distal directionfrom the advanced position to the retracted position causes a pin toride along a track to rotate the annular rotating collar about thelongitudinal axis of the cylindrical housing.
 21. The auto-injector ofclaim 17, wherein only the inwardly angled protrusion of the syringeretainer retains the syringe in the proximal direction, the syringeretainer being engaged with an inward protrusion of the cylindricalhousing to limit proximal movement of the syringe retainer relative tothe cylindrical housing.
 22. An auto-injector comprising: a cylindricalhousing containing a syringe that contains a medicament, the syringecomprising a stopper slidably disposed within a body of the syringe, thestopper forming a fluid tight seal with the body of the syringe; aplunger rod configured to engage the stopper for dispensing themedicament from the syringe; a compression drive spring configured tobias the plunger rod in a proximal direction to dispense the medicamentfrom the syringe; a needle shroud slidable (i) in a distal directionrelative to the cylindrical housing from an advanced position to aretracted position and (ii) in the proximal direction relative to thecylindrical housing from the retracted position to a locked position; aneedle shroud spring configured to bias the needle shroud in theproximal direction relative the cylindrical housing; an annular rotatingcollar rotatably arranged within the cylindrical housing, the annularrotating collar being configured to engage the needle shroud in a mannersuch that a distal translation of the needle shroud causes the annularrotating collar to rotate about a longitudinal axis of the cylindricalhousing; and a syringe retainer releasably disposed within thecylindrical housing, the syringe retainer defining a cavity in which thesyringe is disposed, the syringe retainer comprising an inwardly angledprotrusion that is located at a proximal end of the syringe retainer andthat is engaged with a proximal end of the body of the syringe, thesyringe retainer being sized such that a distal end of the syringeextends distally beyond a distal end of the syringe retainer and adistal flange of the syringe is distally spaced apart from the syringeretainer while the proximal end of the body of the syringe is engagedwith the inwardly angled protrusion of the syringe retainer.
 23. Theauto-injector of claim 22, further comprising a sleeve comprising aflexible arm having a surface that is configured to be releasablycoupled to the plunger rod, the sleeve having a first state in which thesurface of the flexible arm is held in engagement with a surface of theplunger rod to prevent the plunger rod from moving proximally under aforce of the compression drive spring, and the sleeve having a secondstate in which the surface of the flexible arm is deflected in anoutward direction to allow the plunger rod to move proximally under theforce of the compression drive spring to dispense the medicament. 24.The auto-injector of claim 22, wherein the syringe retainer isconfigured to slide relative to the cylindrical housing in the proximaldirection until the syringe retainer engages an inward protrusion of thecylindrical housing such that further proximal movement of the syringeretainer relative to the cylindrical housing is prevented, the inwardprotrusion of the cylindrical housing being integrally formed with thecylindrical housing and extending from a proximal portion of thecylindrical housing.
 25. A method comprising: engaging a syringeretainer of an auto-injector with an inward protrusion of a cylindricalhousing of the auto-injector to limit proximal movement of the syringeretainer relative to the cylindrical housing; engaging a proximal end ofa body of a syringe with an inwardly angled protrusion of the syringeretainer to limit proximal movement of the syringe relative to thesyringe retainer, the syringe containing a medicament, the inwardlyangled protrusion being located at a proximal end of the syringeretainer, the syringe retainer being sized such that when the body ofthe syringe is engaged with the inwardly angled protrusion of thesyringe retainer, a distal end of the syringe extends distally beyond adistal end of the syringe retainer and a distal flange of the syringe isdistally spaced apart from the syringe retainer; holding an angledsurface of a flexible arm of a sleeve of the auto-injector in engagementwith a surface of a plunger rod of the auto-injector to prevent theplunger rod from moving proximally under a force of a compression drivespring of the auto-injector; distally sliding a needle shroud against abias of a needle shroud spring of the auto-injector in a distaldirection relative to the cylindrical housing from an advanced positionto a retracted position thereby moving a pin along a track to rotate anannular rotating collar of the auto-injector about a longitudinal axisof the cylindrical housing, the needle shroud comprising a proximal endportion terminating in an annular flange and two distally projectingarms extending distally from the proximal end portion; and releasing theengagement of the angled surface of the flexible arm with the surface ofthe plunger rod thereby allowing the plunger rod to move proximallyunder the force of the compression drive spring of the auto-injector todispense the medicament from the syringe.
 26. The method of claim 25,comprising deflecting the flexible arm in an outward direction out ofengagement with the surface of the plunger rod to release the engagementof the angled surface of the flexible arm with the surface of theplunger rod.
 27. The method of claim 25, comprising proximally movingthe needle shroud in a proximal direction relative to the cylindricalhousing from the retracted position to a locked position, wherein aproximal end of the needle shroud proximally extends beyond a proximalend of an injection needle of the syringe when the needle shroud is inthe advanced position, the proximal end of the injection needleproximally extends beyond the proximal end of the needle shroud when theneedle shroud is in the retracted position, and the proximal end of theneedle shroud proximally extends beyond the proximal end of theinjection needle when the needle shroud is in the locked position. 28.The method of claim 27, wherein proximally moving the needle shroud inthe proximal direction relative to the cylindrical housing causes aninward projection of the cylindrical housing to slide relative to theneedle shroud within an opening of the needle shroud.
 29. The method ofclaim 27, comprising sliding the needle shroud over a ramp as the needleshroud slides in the proximal direction from the retracted position tothe locked position.
 30. The method of claim 29, comprising preventingdistal movement of the needle shroud relative to the cylindrical housingafter the needle shroud has proximally slid over the ramp.